1. Field of the Invention
The present invention relates to a plasma film deposition method for depositing a film on the surface of a base member through the interaction of a first liquid-phase raw material and a second liquid-phase raw material.
2. Description of the Related Art
It has been the general practice in the art of film deposition to deposit films such as protective films, functional films, etc. on the surface of base members made of plastic, metal, or ceramics. Plasma film deposition technology that uses plasma has heretofore been known as one of the film deposition processes.
Plasma film deposition is carried out by a plasma film deposition apparatus which includes a chamber provided with a high-vacuum pump, etc. Recently, it has been proposed to perform a plasma film deposition process under the atmospheric pressure. For example, Japanese Laid-Open Patent Publication No. 06-002149 discloses a technology for supplying a gas-phase film deposition raw material (gas-phase raw material) to a plasma generated on the surface of a base member and polymerizing the gas-phase raw material which is activated into a film deposited on the surface of the base member.
Japanese Patent No. 4082905 discloses a technology for polymerizing a gas-phase raw material with a plasma generated in a plasma generating apparatus and bringing the polymerized gas-phase raw material into contact with a base member to deposit a film thereon.
Each of the technologies disclosed in Japanese Laid-Open Patent Publication No. 06-002149 and Japanese Patent No. 4082905 uses a gas-phase raw material. However, only part of the gas-phase raw material contributes to film deposition, and most of the gas-phase raw material is carried and discharged by a plasmatized electric discharge gas. Consequently, the rate of film deposition is low, and the efficiency with which the gas-phase raw material is used is low.
It is also known to use a liquid-phase film deposition raw material (liquid-phase raw material). For example, Japanese Laid-Open Patent Publication No. 2007-031550 discloses a technology for mixing a liquid-phase raw material which has been ultrasonically atomized with a gas to produce a mixed mist, and plasmatizing the mixed mist. When the mixed mist is plasmatized, the gas serves as a plasmatized electric discharge gas (excited species), and the liquid-phase raw material is activated.
Japanese Laid-Open Patent Publication No. 2008-504442 (PCT) discloses a technology for electrohydrodynamically spraying a liquid-phase raw material onto a substrate and reacting excited species (a plasmatized electric discharge gas or a gas-phase raw material) which are produced by a plasma or the like.
According to the technologies disclosed in Japanese Laid-Open Patent Publication No. 2007-031550 and Japanese Laid-Open Patent Publication No. 2008-504442 (PCT), it is difficult to control the ratio of the supplied liquid-phase raw material and the excited species which could interact with the liquid-phase raw material. If the excited species run short, then the liquid-phase raw material is activated insufficiently.
On the other hand, if the excited species are excessive, then the liquid-phase raw material is activated excessively. In this case, if the liquid-phase raw material is polymerizable, then its polymerization progresses in a short time, tending to produce minute particles that remain on the film. The minute particles on the film make the appearance of the film poor, and are likely to prevent the film from performing its desired functions.
If the ratio of the liquid-phase raw material and the excited species is a balanced ratio in order to avoid the above difficulties, then it is not easy to increase the rate of film deposition.